#include <stdint.h>

#ifndef DIVINE_HASH_H
#define DIVINE_HASH_H

/* -------------------------------------------------------------------------------
   hashlittle() -- hash a variable-length key into a 32-bit value
   k       : the key (the unaligned variable-length array of bytes)
   length  : the length of the key, counting by bytes
   initval : can be any 4-byte value
   Returns a 32-bit value.  Every bit of the key affects every bit of
   the return value.  Two keys differing by one or two bits will have
   totally different hash values.

   The best hash table sizes are powers of 2.  There is no need to do
   mod a prime (mod is sooo slow!).  If you need less than 32 bits,
   use a bitmask.  For example, if you need only 10 bits, do
       h = (h & hashmask(10));
   In which case, the hash table should have hashsize(10) elements.

   If you are hashing n strings (uint8_t **)k, do it like this:
       for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);

   By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
   code any way you wish, private, educational, or commercial.  It's free.
   ------------------------------------------------------------------------------- */

#if (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && \
     __BYTE_ORDER == __LITTLE_ENDIAN) || \
    (defined(i386) || defined(__i386__) || defined(__i486__) || \
     defined(__i586__) || defined(__i686__) || defined(vax) || defined(MIPSEL))
# define HASH_LITTLE_ENDIAN 1
# define HASH_BIG_ENDIAN 0
#elif (defined(__BYTE_ORDER) && defined(__BIG_ENDIAN) && \
       __BYTE_ORDER == __BIG_ENDIAN) || \
      (defined(sparc) || defined(POWERPC) || defined(mc68000) || defined(sel))
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 1
#else
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 0
#endif

#define hashsize(n) ((uint32_t)1<<(n))
#define hashmask(n) (hashsize(n)-1)
#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))

#define mix(a,b,c) \
{ \
  a -= c;  a ^= rot(c, 4);  c += b; \
  b -= a;  b ^= rot(a, 6);  a += c; \
  c -= b;  c ^= rot(b, 8);  b += a; \
  a -= c;  a ^= rot(c,16);  c += b; \
  b -= a;  b ^= rot(a,19);  a += c; \
  c -= b;  c ^= rot(b, 4);  b += a; \
}

#define final(a,b,c) \
{ \
  c ^= b; c -= rot(b,14); \
  a ^= c; a -= rot(c,11); \
  b ^= a; b -= rot(a,25); \
  c ^= b; c -= rot(b,16); \
  a ^= c; a -= rot(c,4);  \
  b ^= a; b -= rot(a,14); \
  c ^= b; c -= rot(b,24); \
}

inline static uint32_t jenkins3( const void *key, size_t length, uint32_t initval )
{
    uint32_t a,b,c;                                          /* internal state */
    union { const void *ptr; size_t i; } u;     /* needed for Mac Powerbook G4 */

    /* Set up the internal state */
    a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;

    u.ptr = key;
    if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
        const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
        const uint8_t  *k8;
            
        /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
        while (length > 12)
            {
                a += k[0];
                b += k[1];
                c += k[2];
                mix(a,b,c);
                length -= 12;
                k += 3;
            }

        /*----------------------------- handle the last (probably partial) block */
        /* 
         * 'k[2]&0xffffff' actually reads beyond the end of the string, but
         * then masks off the part it's not allowed to read.  Because the
         * string is aligned, the masked-off tail is in the same word as the
         * rest of the string.  Every machine with memory protection I've seen
         * does it on word boundaries, so is OK with this.  But VALGRIND will
         * still catch it and complain.  The masking trick does make the hash
         * noticably faster for short strings (like English words).
         */
#ifndef VALGRIND

        switch(length)
            {
            case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
            case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
            case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
            case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
            case 8 : b+=k[1]; a+=k[0]; break;
            case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
            case 6 : b+=k[1]&0xffff; a+=k[0]; break;
            case 5 : b+=k[1]&0xff; a+=k[0]; break;
            case 4 : a+=k[0]; break;
            case 3 : a+=k[0]&0xffffff; break;
            case 2 : a+=k[0]&0xffff; break;
            case 1 : a+=k[0]&0xff; break;
            case 0 : return c;              /* zero length strings require no mixing */
            }

#else /* make valgrind happy */

        k8 = (const uint8_t *)k;
        switch(length)
            {
            case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
            case 11: c+=((uint32_t)k8[10])<<16;  /* fall through */
            case 10: c+=((uint32_t)k8[9])<<8;    /* fall through */
            case 9 : c+=k8[8];                   /* fall through */
            case 8 : b+=k[1]; a+=k[0]; break;
            case 7 : b+=((uint32_t)k8[6])<<16;   /* fall through */
            case 6 : b+=((uint32_t)k8[5])<<8;    /* fall through */
            case 5 : b+=k8[4];                   /* fall through */
            case 4 : a+=k[0]; break;
            case 3 : a+=((uint32_t)k8[2])<<16;   /* fall through */
            case 2 : a+=((uint32_t)k8[1])<<8;    /* fall through */
            case 1 : a+=k8[0]; break;
            case 0 : return c;
            }

#endif /* !valgrind */

    } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
        const uint16_t *k = (const uint16_t *)key;         /* read 16-bit chunks */
        const uint8_t  *k8;

        /*--------------- all but last block: aligned reads and different mixing */
        while (length > 12)
            {
                a += k[0] + (((uint32_t)k[1])<<16);
                b += k[2] + (((uint32_t)k[3])<<16);
                c += k[4] + (((uint32_t)k[5])<<16);
                mix(a,b,c);
                length -= 12;
                k += 6;
            }

        /*----------------------------- handle the last (probably partial) block */
        k8 = (const uint8_t *)k;
        switch(length)
            {
            case 12: c+=k[4]+(((uint32_t)k[5])<<16);
                b+=k[2]+(((uint32_t)k[3])<<16);
                a+=k[0]+(((uint32_t)k[1])<<16);
                break;
            case 11: c+=((uint32_t)k8[10])<<16;     /* fall through */
            case 10: c+=k[4];
                b+=k[2]+(((uint32_t)k[3])<<16);
                a+=k[0]+(((uint32_t)k[1])<<16);
                break;
            case 9 : c+=k8[8];                      /* fall through */
            case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
                a+=k[0]+(((uint32_t)k[1])<<16);
                break;
            case 7 : b+=((uint32_t)k8[6])<<16;      /* fall through */
            case 6 : b+=k[2];
                a+=k[0]+(((uint32_t)k[1])<<16);
                break;
            case 5 : b+=k8[4];                      /* fall through */
            case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
                break;
            case 3 : a+=((uint32_t)k8[2])<<16;      /* fall through */
            case 2 : a+=k[0];
                break;
            case 1 : a+=k8[0];
                break;
            case 0 : return c;                     /* zero length requires no mixing */
            }

    } else {                        /* need to read the key one byte at a time */

        const uint8_t *k = (const uint8_t *)key;

        /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
        while (length > 12)
            {
                a += k[0];
                a += ((uint32_t)k[1])<<8;
                a += ((uint32_t)k[2])<<16;
                a += ((uint32_t)k[3])<<24;
                b += k[4];
                b += ((uint32_t)k[5])<<8;
                b += ((uint32_t)k[6])<<16;
                b += ((uint32_t)k[7])<<24;
                c += k[8];
                c += ((uint32_t)k[9])<<8;
                c += ((uint32_t)k[10])<<16;
                c += ((uint32_t)k[11])<<24;
                mix(a,b,c);
                length -= 12;
                k += 12;
            }

        /*-------------------------------- last block: affect all 32 bits of (c) */
        switch(length)                   /* all the case statements fall through */
            {
            case 12: c+=((uint32_t)k[11])<<24;
            case 11: c+=((uint32_t)k[10])<<16;
            case 10: c+=((uint32_t)k[9])<<8;
            case 9 : c+=k[8];
            case 8 : b+=((uint32_t)k[7])<<24;
            case 7 : b+=((uint32_t)k[6])<<16;
            case 6 : b+=((uint32_t)k[5])<<8;
            case 5 : b+=k[4];
            case 4 : a+=((uint32_t)k[3])<<24;
            case 3 : a+=((uint32_t)k[2])<<16;
            case 2 : a+=((uint32_t)k[1])<<8;
            case 1 : a+=k[0];
                break;
            case 0 : return c;
            }
    }

    final(a,b,c);
    return c;
}
#undef hashsize
#undef hashmask
#undef final
#undef mix
#undef rot

#endif
